High-Definition Multimedia Interface (HDMI) is a compact audio/video interface standard for transmitting and receiving uncompressed digital data. The HDMI standard enables the connection of a digital audio/video source (e.g., set-top box, Digital Video Disc (DVD) player, camcorder, personal computer, video game console, and audio/video receiver) to a compatible digital audio/video sink device (e.g., computer monitor, video projector, and digital television). The device that sends an HDMI signal (e.g., the DVD player or set-top box) is the HDMI source device, and the device that receives an HDMI signal (e.g., the digital television) is the HDMI sink device.
The HDMI specification describes three separate communications channels, Transition Minimized Differential Signaling (TMDS), Display Data Channel (DDC), and Consumer Electronics Control (CEC). The TMDS communications channel carries all audio and video data as well as auxiliary data that describes the active audio and video streams. An HDMI source device uses the DDC communications channel to determine the capabilities and characteristics of the HDMI sink device by reading the Enhanced Extended Display Identification Data (E-EDID) data structure. The HDMI source device reads the E-EDID from the HDMI sink device, and delivers only the audio and video formats that the HDMI sink device will support. In addition, the HDMI sink device detects and processes the received audio and video data appropriately. The CEC communications channel is optional, and provides support for higher-level user functions such as automatic setup tasks or tasks typically associated with infrared remote control usage.
Consumer electronics devices that support the HDMI standard can be automatically configured, self-correct errors, and free the consumer from managing the device. The goal of the HDMI standard is for these devices to be “plug-n-play” devices. Unfortunately, the plug-n-play process for HDMI devices has never worked smoothly. The HDMI source devices must interoperate with many types of HDMI sink devices and the presentation output has many possible formats in the HDMI standard. Interoperability problems arise largely due to the limited HDMI High-bandwidth Digital Content Protection (HDMI/HDCP) compliance test scope as specified by the HDMI/HDCP standard bodies. For example, the HDCP compliance test uses only the 480p output format. It is possible for some digital televisions to pass the compliance test using the 480p output format, but still exhibit interoperability problems on other formats such as the 480i output format. Furthermore, the HDMI compliance test does not involve any transition characterization, leaving room for a wide variety of transition behaviors during video presentation.
If there is a bug or flaw in the design of the HDMI sink device that results in poor behavior in some output formats, the automatically selected plug-n-play configuration will offer no work-around. For example, it is not possible for many digital television users to upgrade their television, even if a firmware fix is available. The cable and satellite system operators rely on the manufacturers of the set-top box to provide a work-around for all of the interoperability issues with firmware upgrades to the set-top box. The challenge is to provide a set-top firmware work-around for a specific model of television without affecting the operation—and previous work-around—for all other models of television. A perfect compromise solution is hard to achieve and deployment results in reduced presentation quality for all models of television. In addition, frequent changes to the firmware on the set-top box significantly increase the burden of testing the firmware release.
Another significant challenge is the constant appearance of new HDMI sink devices that have never been tested with the HDMI source device. An HDMI source device, such as a set-top box, is exposed to almost every new HDMI television sink device being manufactured. There is no way to avoid the inevitable interoperability issues that arise. When confronted with many consumer complaints, the cable and satellite system operators once again rely on the manufacturers of the set-top box to provide a work-around for all of the interoperability issues with firmware upgrades to the set-top box.
There is a need for an HDMI sink device interoperability evaluation process that determines the best configuration of HDMI source device output parameters for communicating with a particular HDMI sink device. After evaluating the HDMI sink device, the process saves the configuration for all future connections with the same HDMI sink device. This evaluation process will allow the HDMI source devices to optimize the output parameter settings for each HDMI sink device without requiring a compromise solution that affects other HDMI sink devices. The presently disclosed invention satisfies this demand.